The approach to nonsustained ventricular tachycardia (NSVT), defined as three or more consecutive ventricular complexes at rates greater than 100 beats/min, terminating spontaneously within 30 seconds, is distinct from most other arrhythmias managed by clinicians. Most arrhythmias come to a clinician's attention because they cause symptoms such as palpitations, chest discomfort, presyncope, or syncope. Although NSVT may be associated with symptoms, it is most often an asymptomatic finding discovered by electrocardiogram (ECG) monitoring. In this respect, NSVT creates an unusual dilemma for the clinician, who must address the following questions: (1) Is the patient symptomatic from the NSVT? (2) What are the prognostic implications of NSVT in this patient? (3) What interventions are warranted in the asymptomatic patient?

NSVT sometimes is an important marker of increased risk for subsequent tachyarrhythmias capable of causing syncope, cardiac arrest, or sudden cardiac death (SCD). It is not clear whether episodes of NSVT bear a cause-and-effect relationship with sustained tachyarrhythmias and SCD, or if they simply are a surrogate marker of cardiac dysfunction and electric instability. It is clear, however, that the prognostic significance of NSVT depends on the presence, type, and severity of underlying heart disease. To treat asymptomatic and symptomatic patients with NSVT properly, the clinician first must have a thorough understanding of the underlying cardiac substrate in a particular patient. The prognosis hinges on whether this is a patient with a structurally normal heart, coronary artery disease with prior myocardial infarction, a nonischemic dilated cardiomyopathy (NIDCM), or a hypertrophic cardiomyopathy (HCM). Knowing the anatomic substrate as well as overall left ventricular systolic function determines the prognostic significance of the NSVT, the potential role of programmed stimulation (electrophysiology study), and the appropriate management of the patient.